Carburetor structure



Nov. '11, 1941. G." M. BICKNELL 2,262,632

CARBURETOR STRUCTURE Filed March '26, 1940 ,7 MM v FF J- INVENTOR GEORGE M. BICKNELL @WMM ATTORNEY Patented Nov. 11, 1941 UNITED STATES PATENT OFFICE CARBURETOR. STRUCTURE George M. Bicknell, St. Louis, Mo., assignor to Carter Carburetor Corporation, St. Louis, Mo., a corporation of Delaware Application March 26, 1940, Serial No. 325,966

1 Claim. '(Cl. 26163) This invention relates to carburetors for injointly by the carburetor throttle valve and by suction posterior to the throttle valve is mounted on the body of the carburetor itself. In this device, particularly during the starting operation, a relatively large quantity of air is drawn through the starting device and into the carburetor, which volume of air, after the engine has started and the throttle is released, serves to lift a ball or plunger to a position to render the throttle control of the starting switch ineffective. The large volume 'of air drawn into the carburetor during starting produces an annoying sucking or whistling sound.

It is an object of the present invention to eliminate the noise so produced.

These and other more detailed objects hereafter appearing are attained substantially by the structure illustrated in the accompanying drawing in which: a

Fig. 1 is a side view of a carburetor and portions of the associated engine manifolding, parts of the carburetor being broken away and sectioned for clearer disclosure.

Fig. 2 is a detail sectional view taken substantially on line 2-2 of Fig. l.

The carburetor illustrated in Fig. 1 includes a downdraft mixture conduit formed of an air inlet horn I at the upper end, an intermediate mixing chamber 2 enclosing venturis 3 and an outlet portion 4 at the lower end having flange 5' bolted to hot spot 6 communicating with the intake manifold (not shown) and exhaust manifold l.

Adjacent the mixture conduit or barrel portion of the carburetor is a bowl [0 within which fuel is maintained at a constant level, preferably by well known float and needle mechanism (not shown). Fuel is supplied to the mixture conduit from thebowl l0 through the main nozzle ll. Hot gases from exhaust manifold l circulate through hot spot 6, as is well known, for heating the fuel and air mixture supplied by the carburetor.

An unbalanced choke valve I2 is pivoted in air horn l on shaft i3 which has one end protruding beyond the air horn and into an insulated cylindrical housing i4 secured to one side of the air horn. A thermo-sensitive, bi-metallic coil I5 is enclosed in housing I4 and is secured at its inner end to a pintle i6 projecting inwardly from the cover of the housing. The outer end of coil i5 is hooked, as at H for engaging a finger i8 on curved crank l9 secured at one end to the end of choke shaft l3 within the housing. The other end of crank i9 is secured by a link to a piston 2i slidably received in a small cylinder 22 within the housing. Cylinder 22 at its lower end communicates through its suction passage 23 with a portion of the carburetor mixture conduit posterior to the usual throttle valve 24 mounted on throttle shaft 25. The portion of the suction passage communicating with the mixture conduit is formed by a separate tube 26 extending from passage 23 inwardly substantially beyond the conduit wall. The open end of tube 26 preferably faces directly across the conduit or, in other words, parallels the axis of the mixture conduit. The tube is inserted through the outlet end of the carburetor barrel and is preferably pressed into position.

A stove 21 is secured to exhaust manifold i and is connected to housing l4 by means of a tube 28. The stove is in constant communication with the atmosphere through the slot 29 and serves to confine a body of air to be heated by the hot exhaust gases. Cylinder 22 into which piston 2i loosely fits, is provided with longitudinal grooves 30 in the inner wall thereof so that a portion of the suction communicated to the cylinder escapes past the piston and is available for drawing air from the stove past the thermostat and thence into the mixture conduit. Automatic choke control mechanism of the type herein shown is more fully disclosed and claimed in a Patent #2,085,351 issued in the name of. Irven E. Coffey.

Mounted on the carburetor body is a starting device which includes a chamber formed in the mixture conduit wall and cormnunicating with the atmosphere, at its lower extremity, by means of an opening 36. At its upper extremity, this chamber connects by means of a duct 31 with automatic choke suction passages 23 and thence communicates with the mixture conduit through projecting tube 26.

One end of throttle shaft 25 is cut away to form a semi-circular section 25a as shown in Fig. 2. Extending outwardly and upwardly from chamber 35 adjacent throttle shaft section 250; is a second chamber 38 which slidably receives a plunger I! having a dished inner end ll. The outer end or plunger 3! is adapted to telescopingly receive a short shaft ll carrying a resilient switch blade 42, outward movement of plunger I! being resisted by a spring 0 in insulator cap 44. Cap 44 is of suitable insulating material, such as Bakelite or hardrubber, and mounts threaded bushing ll receiving terminal screws 48 under the heads oi which are securedterminal clips 41. Bushings ll extend entirely through insulating cap 44 and are disposed ,to be engaged by switch blade element ll when the latter is propelled outwardly.

Loosely received in chamber 3! is a ball 48 which, when the carburetor is inactive, and the throttle closed, lodges between the protecting, dished end of plunger SI and section Ila at the end 01' the throttle shaft;- When the throttle is then opened, as for starting, throttle shaft element 25a, ball Cl, and plunger 39 cooperate to force switch blade 2 to close the starter switch. During this operation, the substantialvolume of a air sucked past the ball through passage 23, due

to cranking of the engine, both from the thermostat housing and throughchamber 40, but for tube 20 extending into the mixture conduit,

would produce a very noticeable and objection-' I have found that by projecting suction passage 23 into the mixture conduit as by means of tube 20, and out of the direct path of the downward current or air passing between the edge of the throttle disc and the mixture conduit wall, the outlet of passage 23 and the air stream emerging therefrom is shielded by the throttle and the objectionable noise is entirely eliminated. The invention has utility in other associations than those shown. Obviously, the carburetor.

minating substantially flush with the inner wall thereof posterior to the'throttle, and its outer end exposed to an atmospheric zone outside said conduit, said duct forming an open communication between said conduit and said zone whereby a stream of air flows through said duct into said conduit, an extension tube for the inner end of said duct attached to the wall of the mixture conduit for extending the duct inwardly of said wall whereby said throttle will partially shield the duct extremity to prevent the conflicting currents of the air streams causing undesirable noise at the duct ope GEORGE M. BICK'NELL. 

